壁面矩形微尺度结构对高速稀薄剪切流的影响  

Effects of rectangular micro-scale structures on hypersonic rarefied shear flow

作　　者：刘艳婷 欧吉辉 韩宇峰 陈杰 LIU Yanting;OU Jihui;HAN Yufeng;CHEN Jie(School of Mechanical Engineering,Tianjin University,Tianjin 300072,China)

机构地区：[1]天津大学机械工程学院,天津300072

出　　处：《航空学报》2023年第16期65-84,共20页Acta Aeronautica et Astronautica Sinica

基　　金：国家自然科学基金(92152103);天津市自然科学基金(20JCQNJC01240)。

摘　　要：高超声速飞行器表面往往存在复杂的粗糙结构,其尺度与临近空间飞行器来流分子平均自由程大约在同一量级,此时壁面微尺度结构将显著影响近壁区流动特征以及壁面气动力/热。将壁面粗糙结构简化为周期分布的矩形粗糙元,采用直接模拟Monte Carlo(DSMC)方法研究了壁面粗糙元高度、壁面适应系数对高速稀薄剪切流流场特性及壁面气动特性的影响。结果表明:相比于光滑壁面,粗糙壁近壁区气体速度减小、温度降低,壁面总阻力、热载荷增加。壁面粗糙结构增强了气体分子和壁面间的动量、能量交换,这种增强效应随着粗糙元高度的增加而增加,当粗糙元高度增加到分子平均自由程时,整个凹腔内形成旋涡结构,此后粗糙元高度的影响不再明显。此外,壁面适应系数和壁面粗糙结构对近壁区流动存在耦合效应,壁面适应系数越小,粗糙结构对气固间动量、能量交换的促进作用越明显。Complex micro-scale roughness structures usually exist on the surface of hypersonic vehicles.With their scale of roughness almost in the same order as the mean free path of gas molecules for vehicles in near space,these microstructures will significantly affect the flow characteristics in the near surface region and surface aerodynamics.In this paper,a high-speed shear flow between a smooth wall and a rough wall,where the microstructures are simplified as periodically distributed rectangular elements,is simulated using the Direct Simulation Monte Carlo(DSMC)method.The effects of roughness element heights and surface accommodation coefficients are investigated.The re⁃sults show that the microstructures enhance the momentum and energy exchanges between gas and surface.Com⁃pared with a smooth surface,the gas velocity and temperature near the rough surface decrease while the total drag and heat load increase.As the element height increases,the effects of roughness become stronger.When the rough⁃ness height is larger than one mean free path,a vortex between roughness elements is fully formed and the effect is no longer sensitive to the element height.The microstructures and surface accommodation coefficients have a cou⁃pling effect on the momentum and energy exchange.Smaller accommodation coefficients lead to stronger enhanced effect induced by roughness.

关 键 词：微尺度结构 DSMC方法 稀薄气体效应 高速剪切流 适应系数 

分 类 号：V19[航空宇航科学与技术—人机与环境工程]